“Multivariate climate change can favor large herbivore body size in food webs”
Lauren M. Smith-Ramesh, Adam E. Rosenblatt, and Oswald J. Schmitz (Mar 2018)
Climate change may drive shifts towards larger herbivore body size
Scientists have generally expected animals to get smaller as the planet warms, based on relationships between animal growth and development and temperature. However, global climate change means more than just warmer temperatures: other climate factors such as atmospheric carbon dioxide and rainfall patterns are also expected to change. Smith-Ramesh et al. have constructed a model based on food web interactions amongst old-field plants, grasshoppers, and spiders exposed to multiple changing climate variables. They find that under certain predicted future scenarios, climate change could actually result in larger animal body sizes. These results challenge past assumptions that climate change will result in smaller animals across the board.
Climate change is expected to favor smaller-bodied organisms through effects of temperature on physiological performance and food-web interactions, so much so that smaller body size has been touted as a universal response to global warming alongside range-shifts and changing phenology. However, climate change involves more than warming. It is multivariate, and the interplay between climate variables may result in less straightforward predictions. We present a model that considers the simultaneous effect of multiple variables (temperature, CO2, and moisture) on herbivore body sizes within a tri-trophic food web comprised of vegetation, herbivores, and a shared predator. The model accounts for climate effects on animal behavior, plant and animal metabolism, and plant quality to explore emergent effects on herbivore body size. Our analysis reveals that some common multivariate climate change scenarios may favor larger-bodied herbivores, challenging previous findings of shifts toward small-bodied herbivores in the face of rising temperatures.